Example embodiments relate to a forming a dielectric layer pattern and a method of manufacturing a flash memory cell using the same. More particularly, example embodiments relate to forming a dielectric layer pattern including a metal oxide having a high dielectric constant and a method of manufacturing a flash memory cell using the same.
Semiconductor memory devices may be divided into volatile memory devices and non-volatile memory devices. A volatile memory device, e.g., a dynamic random access memory (DRAM) device or a static random access memory (SRAM) device, may have a relatively rapid access time but may lose stored data over time. On the other hand, a non-volatile memory device, e.g., a flash memory device or an electrically erasable programmable read-only memory (EEPROM) device, may store data for a long time but may have a relatively slow access time. Flash memory devices may be widely employed in various electronic devices, e.g., cellular phones, MP3 players, USB memory devices, and so forth.
In a conventional flash memory device, data may be electrically stored in or erased from the flash memory device through Fowler-Nordheim tunneling or channel hot electron injection. The flash memory device may be classified as either a floating gate type non-volatile memory device, or a SONOS (silicon oxide nitride oxide semiconductor or a MONOS (metal oxide nitride oxide semiconductor) type non-volatile memory device.
The floating gate type non-volatile memory device may include a tunnel oxide layer, a floating gate electrode, a blocking dielectric layer and a control gate electrode. For example, a multilayer dielectric layer including a lower silicon oxide layer, a silicon insulation layer and an upper silicon oxide layer may be used for the blocking dielectric layer.
Recently, in order to increase the capacitance of the blocking layer dielectric layer and improve leakage current properties, a method of forming the blocking dielectric layer using a high dielectric material has been presented. For example, the blocking dielectric layer may be formed using a metal oxide such as hafnium oxide, zirconium oxide, aluminum oxide, hafnium aluminum oxide, etc., having a higher dielectric constant than silicon nitride.
In order to form a gate structure including the blocking dielectric layer with the high dielectric material, a patterning process of patterning the control gate electrode layer, the blocking dielectric layer and the floating gate electrode may be performed. However, an anisotropic etch process may not be easily performed over the blocking dielectric layer having the high dielectric material.
Accordingly, the blocking dielectric layer may not be easily removed with a high etch rate, without damaging adjacent other layers. Further, during the etching process for etching the blocking dielectric layer, a microloading effect may be large, so that an etch rate of the blocking dielectric layer may differ greatly from an etch rate of the adjacent exposed layers. Further, because the blocking dielectric layer may be conformally formed on an upper surface and sidewalls of the floating gate electrode, portions of the blocking dielectric layer, which is formed on the sidewalls of the floating gate electrode, to be etched by the anisotropic process may be very thick. Accordingly, it may not be easy to completely remove the blocking dielectric layer through the anisotropic etch process, without damaging adjacent layers.
On the other hand, if the blocking dielectric layer to be removed still remains after performing the dry etch process, the floating gate electrode under the remaining blocking dielectric layer may not be removed by a following process, to thereby cause a stringer failure where adjacent cells short one another. Further, if the blocking dielectric layer is excessively etched to completely remove the blocking dielectric layer, the floating gate electrode and the isolation layer may be excessively etched, thereby damaging the middle portion of an active region under the floating gate electrode and the peripheral portion of the active region on both sides of the isolation layer pattern.
Therefore, a method of patterning a gate structure of a non-volatile memory device using a high dielectric material as the blocking dielectric layer and capable of reducing damage to the active region or a stringer is desired.